Electric-furnace control apparatus.



J. A. SEEDE.

ELECTBIC FURNACE CONTROL AP'PARATUS.

APPLICATION FILED APR. Iz. 1916.

l ,206,603. Pzfented Nov. 28, 1916.

IT'WVEYTLOPZ John JSeede, ba

His ftornea.

D -as PATENT OFFICE.

JOHN A. SEEDE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A COBPORATION OF NEW YORK.

ELECTEIC-FIBNACE CONTROL APPARATUS.

ecacoa Specfication of Letters Patent.

Patented Nov. 28, 1916..

Applcationfiled April 12, 1916. Seria1 No. 90,765.

To aZZ 'Lu/tom it my concem Be it known that I, JOHN A. SEEDE, a

citizen of the United States, residing at Schenectady, County of Schenectady, State of New York, haVe invented certain new and useful Improvements in Electric-Furnace Control Appa'ratus, ot which the following is a specification.

The present invention conprises a new electric control apparatus for electric furnaces, particularly are furnaces, and its ob'- ject is to move furnace electrodes in response to awariation of current in the electrode circuit and when the desired regulation has been efiected tt) stop the movement of the electrode promptly, without overrunning. due to the inertia of the moving parts. I

V In accordance-with my invention the electrodes are moved -b-y an electric motor controlled, preferably through relays, by a circuit-closing magnet responsive'to variations of power in the t'urnace circuit, and interlocked with a dynamic braking device, which is automatically actuated when the motor is open-circuited. I have also provided a switch for automatically disconnecting the control apparatus, thereby stopping the motor, when the voltage of the furnace supply current falls below a predetermined value. These and other features of my invention will be pointed out' with greater particularity in the appended claims.

'A more complete understanding of my invention may behad from the following description taken in connection with the accompanying drawing which shows diagrammatically a three-phase arc furnace provided witha control apparatus operated by direct current and constructed in accordance with my invention.

Referring to the drawing, the electric furnace is diagrammatically indicated as comprising a receptacle 1 containing a conductive charge 'and having electrodes 3, 4 and 5 between which and the charge arcs are maintained. The electrodes are respectively connected to supply conductors 6, 7 and 8 car- The V motor 9 is mechanically connectedto the electrode-by any form of suitable gearing, the drawing showing a speed-reducing gear 10, drivenbythe motor,'acting as a nut to raise and lower the screw threaded rod ll carrying the electrode `The motor has a continuously excit'ed field 12, which is connected througl' conducto'rs 13'to direct current supply conductors 14 and 15. The motor armature is connected by' c'onductors 16 and 17, to the source of direct current" througha 'control apparatus to' be hereinafter -more fully described for starting, st0p-' ping andreversing the 'motor in accordance' with the variations of current in th'eelectrode .supply conductor 6,

The control apparatus includes relay magnets. lS'and 19,'the circuitsof .which are respectively closed and ,openedbya contactmakingmagne't This magnet is connected to a current transformer 21,-by conductors 22 and is provided with a seriesoftaps 23 over which the switch %may be successively moved for adjusting the responsiveness of the'magnt to any particular desired current val-ue. [The weight of the magnet is balancedby a spring 25 which may be adjusted so the 'magnet will tend toflcome at rest between'contacts 26 and 27 when the current in the electrode supply 'circuit-has a desiredpredetermined' value. When the currentis greater than this value the'magnet core will be pulled down and the switch arm 28 will complete an `elect`rica^l 'circuit' through the contact 27, actuating the relay magnet -18 through conductors 29, 30, 31, 32 and 33. All of the 'Contacts 'in the system have been shown'as being'open, it being assumed that there is no current fiowing. lVith the system active,`the magnet %which .is connected to supply conductors 6 and 8 acrossone of the phases of the supply circuit will have its armature pulled up, closing the` c'ontactor '35. moved over to the contact 37 when it is desired to operate the control mechanism automatically. This switch 36 will be shifted to the contact 38 when it is desired to sub'stitute hand control for automatic control. Returning to the automatic control mechanism, when 'the magnet 18' pulls up it-s armature, the switches 39, 40 are closed completing a circuit through .the motor 9 through the conducto'r 4:1, the switching contact 39,' conductor 42, conductor 17, armature 43, conductor 16, contact 40, and back to the oppo- The switch arm 36 should be site terminal OI" the direct current supply system through the conductor 4:1 in circuit duced to a predetermined value the switch arm 28 will leave the contact 27 causing the relay magnet 18' to become denergized. Both the relay magnets 18 and'19 are connected through mechanical interlocks 17, 48 and 19 to a magnet 50, which is connected to the motor supply conductors 16 and 17. As long as either the magnets 18 or 19 are closed therespective interlock 117 or-aLS will prevent the magnet 50 'rom closing its con-- tact 51, but as soon as these control magnets 18, 19, become denergized the magnet 50 can raise its armature and close the contact 51. As has just been explained above, when the motor has raised the electrode 3 a desired anount, the magnet 18 is open-circuited by the switching magnet 20, and as a count-er-electromotive force generated by the motor 9 isimpressed on the magnet 50 the contact 51 is immediately closed, thereby short-circuiting the motor armature through the resistance This has the effect of dynamically braking the motor and prevents over-running of the electrode. lVhen the supply current becones lower than the predetermined Value, for example, by burning away of the electrode causing a lengthening of the arc, theswitch arm 28 will come into contact with the contact 26 completing a circuit through the control magnet 19 through conductors 29. 30, 53, 54:, and 33, closing Contacts 55 and 56. The closure of these contacts will nechanically open the contact 51 in the dynamic braking crcuit by means of the mechanical interlock 18, and the motor armature will be connected to the supply conductors 14 and 15 through the conductor 57, contact 56, conductors 58, 16, 17, the contact 55 and back to the conductor 15 ot' the supply system through the conductor 11, containing the resistance 46, thereby reversing the motor and causing it to rotate in the opposite direc tion to lower the electrode. hen the electrode has been lowered to an amount which will cause the supply current to increase to a predetermined Value, the switch blade 28 will leave the contact 26 denergizing the relay control magnet 19 and, in the sane manner as above described, will permit of the closure of the contact 51 again automatically braking`the mot-or and preventing over-running of the same.

As already indicated, it maybe desirable in some cases, for example, when the furnace is being started to operate the electrodes by hand control and for this purpose the switch 36 iS moved over to the contact soaece gizing the relaycontrol magnet 19, through the conductors 54:, the switch 59 in its depressed position, the switch (30 in its raised position and the conductors 61 and 29. `lVhen it is desired to raise the electrode, the push button GO is depressed, energizing the control magnet 18, through the conductor 31, the switch (30 in its depressed position, the conductor (32, the switch 59 in its raised position, and the conductors 61 and 29. W'hen the voltage of the turnace supply circuit (3, 7, 8, falls below a predetermined value the relay 31 will become weakened sufiiciently to open the contactor 35, thereby disconnect- 'ing the control apparatus and denergizing the motor, while the Voltage of the furnace supply` below the predetermined Value.

My improved electrode control has been shown containing a controlling switch re.- sponsive 'to Variations of current, but 1 wish this to be considered illustrative of a system responsive to any other electrical condition of a supply cir'cuit for a furnace;

` hat 1 claim as new and desire to secure by Letters Patent of the United States, is,-

1. An apparatus for regulating electric furnaces, comprising an electrode to be shifted, a power circuit for said electrode,

an ,electric motor operatively connected to said electrode, switching means responsive to variations of energy in the electrode circuit 'for controlling and reversing said motor, a brake resistance, and means operative v connections to the notor to produce desired regulation, and an interlock permitting dynamic braking means to operate when the motor 'is denergized.

3. A regulating apparatus for arc furnaces, comprising an electrode, an energy circuit therefor, an electric motor mechani- 'cally connected to said electrode, circuit connections for said motor, a contact-making magnet responsve to raratons of energy in the electrode circuit, relay magnets ener- ,qized by said contact-making magnet for changing the motor crcuit connections to control the motor, and dyna-mic braking means interlocked with said relay magnets to brake the motor when the motor circuit is opened;

4. An apparatus for regulating furnace electrodes comprising an electrode,` an energy circuit theretor, a reversible electric motor tor movng said eleetrode, connections for energzng said motor, control means :for sht'tng eonnections to reversesaid motor. electro-responsve means for operating said control means in accorclance with Varatons of current in the electrode supply crcuit. a resstance, means nterlocked with said control means to close the armature crcut of said motor through saicl resistance to brake the motor when the motor-supply crcut sopen and means 'or disconnectn' the control means, thereby cleenergizing the motor, when the voltae'e of current n the electrode circuit falls below a predetermned value.

5. in apparatus for regulatlng electre turnaces eom-prsng an electrocle, an energy supply crcuit therefor, an electric motor mechanically connected to said' electrocle, eleetromagnetic means, responsve to variaton of energy in the electrode supply circlt, for controlling and rerersing said motor` means for (lynamically braknr said motor, and an electromagnetic cut-out for denergizing said motor when the Voltage of the. electrode supply Circut falls below a prcdeterminecl Value.

(3. An apparatus for regulatinz' electrc *furnaces comprisng` the combinaton of an eleetrie furnace, a furnace energy supply` crcut. an electric motor mechancally connected to a member of said furnace, an energy supply crcuit tor the motor, means responsve to a precletermined Variation of energy in the electrode supply crcut for controllng said motor. and an electromagnetc cutout for denergzng said control means ancl'maintainng the same clenergzed as long` as the voltage in the electrocle supply ercut falls below a predetermned Value.

7. A regulatng* apparatus for electre* furnaces comprising a :furnace energy supply crcut, an electrc furnace, an electrc motor mec'hancallv connected to a member of said furnace, means responsive to Variatons of energy in the supply circut for contnuouslv energzing said motor until a desrecl regulation has been ellected anl means for bral ing` said motor when the (lesred regulation has been e'll ecte l.

8. A regulating apparatus ;tor electrc t'urnaces comprsing a furnace energy supply crcuit, an electric motor for meehancally et'fectng' the. lesirecl regulaton, a separate source of energy for said motor, a control tlevce for Operating' and reversng said motor, a swtching* magnet responsve to variatons of current in the furnace supply cireut for changing the connectons of said control (levce and a cut-out magnet for disconnectng said control (levce when and as long` as the voltage ot' the furnace supply clrcut is below a precleternnnecl Value.

In witness whereofi I hare hereunto set my hand this 11th (lay of Aprl, 1916.

JOHN A. SEEDE. 

